In the combustion of a fuel, such as coal, oil, peat, waste, etc., in a combustion plant, such as a power plant or a waste incineration plant, a hot process gas is generated containing among other components, gaseous pollutants, such as hydrogen chloride (HCl) and sulphur oxides, such as sulphur dioxide (SO2). It is normally necessary to remove at least a portion of the gaseous pollutants from the process gas before the process gas can be released into the atmosphere, or treated further in, for example, a carbon dioxide (CO2) compression plant for transport to a CO2-sequestration plant.
When separating gaseous pollutants, such as hydrochloric acid and sulphur dioxide, from hot process gas, a method is frequently used in which a lime-containing absorbent material is introduced into the process gas to react with the gaseous pollutants. When the absorbent material reacts with the gaseous pollutants, the gaseous pollutants are converted chemically or physically into dust material, which is then separated in a filter. EP 1 815 903 A1 discloses an example of such a method, in which lime-containing dust is mixed with water in a mixer and is then introduced into a contact reactor to react with gaseous pollutants of a hot process gas. The dust material formed by such reaction is separated in a filter and recirculated to the mixer to be mixed again with water for subsequent introduction into the contact reactor.
The dust material formed by reaction of absorbent material with gaseous pollutants may contain some substances, such as calcium chloride, prone to making the dust material sticky, which can cause severe operational disturbances in a gas cleaning plant.